A conventional flat-bed scanner has a movable optical module therein which scans a calibration strip at a fixed position before proceeding scanning so as to obtain multiple scanning lines and according to the scanning lines to calibrate the optical module.
A sheet-fed scanner has a feature of automatically feeding the sheets which are scanned by the optical module in the scanner. Due to the movement of the sheet, the fixed optical module cannot calibrate the color depth for multiple lines before the image scanning. The optical module can only scan single one line to calibrate the color depth. If there is dust or defect at the position of the line to be scanned, the result is incorrect such that the calibration of color for single line scanning has low reliability.
A combination of a flat-bed scanner and sheet-fed scanner may proceed double-side scanning. If the flat-bed scanner has a calibration strip on the optical module thereof, the calibration strip on the optical module of the flat-bed scanner and the optical module of the sheet-fed scanner have relative movement when the optical module of the flat-bed scanner moves to proceed calibration of color. By this way, the optical module of the sheet-fed scanner may have multiple scanning lines on the calibration strip so as to proceed the calibration of color for the multiple scanning lines.
Nevertheless, once the flat-bed scanner and the sheet-fed scanner are separated, and the sheet-fed scanner is used individually, the calibration of color cannot be proceeded. Even they are used in combination, the gap between the two respective optical modules of the sheet-fed scanner and the flat-bed scanner is large, so that the quality of the scanning lines obtained by the optical module on the sheet-fed scanner is not satisfied, and the reliability of the calibration of color is affected.
It is to be noted that the sheet-fed scanner includes a single scanning unit which can be operated independently, and a sheet-fed scanning unit which can be combined with the flat-bed scanner to proceed double-side scanning.